In the last decade, worldwide production of basic food has
increased faster than the total population has grown - about 2.5
per cent per year vs. 1.9 per cent for population increase.
However, in the developing countries, despite a 3.2 per cent
increase in-food production each year, production has barely kept
ahead of the rate of population growth. A variety of factors
underlie the world food problem, and the imbalances between
developed and developing countries. One is avoidable losses of
food crops. After all the effort devoted to produce food, it is
of utmost importance to handle it carefully after harvest.

For this reason, priority should be given to post-harvest
studies, particularly in humid tropical climates where at least
half of the food supply from plants and animals may be lost
between harvest and consumption. The magnitude of these losses
can only be estimated, because so few assessments are available.
For grain crops, the conservative estimate is that at least 10
per cent are lost after harvest in developing countries, and
losses up to 40 per cent have been recorded. These losses are
classified in Table 1.

A reduction of these losses by half could provide for almost
50 per cent of the food-grain import requirements of developing
countries by 1985, at a value of about $US 8 billion. Losses may
be either in quantity or quality, or both. Losses in quantity are
more easily determined; for example, the difference in weight of
grains infested with insects. However, deterioration of nutritive
quality is often overlooked and is more difficult to determine.

THE DIMENSIONS AND CAUSES OF THE PROBLEM

Low agricultural yields have been blamed for world food
problems, but can we continue to emphasize only agricultural
production when an average of 30 per cent of the crops raised
never reaches the consumer? Damage caused by insects, rodents, or
birds varies extensively in different areas, particularly with
respect to cereals and oilseeds. Insects and rodents are the
principal causes of losses of stored cereals or legumes in
tropical or subtropical countries and the speed with which many
insect species multiply is influenced by the moisture content of
a particular commodity.

Micro-organisms, such as bacteria or fungi, are responsible
for most of the losses of perishable products such as fruits and
vegetables. Fungi in particular attack cereals as well as fruits
and vegetables, and contribute to both quantitative as well as
qualitative loss in food value and a decrease in the monetary
value of the crops. Another serious concern is that certain
species of fungi produce metabolic toxins, or microtoxins, for
example the aflatoxin produced by Aspergillus flavus, that
renders a product dangerous for both human and animal
consumption.

Information on post-harvest losses is still very inconsistent
and scarce, especially for fruit and vegetable crops, for which
losses are much larger than those of cereal crops. A recent study
done in the State of Sao Paulo, Brazil, indicated that out of 23
food products, 6 kinds of fruits and vegetables accounted for
10.6 per cent to 13.3 per cent of the total food expenses of
2,380 families interviewed. From an economic point of view,
tropical fruit losses are important both for these families and
for their export potential. In Sao Paulo, horticultural crop
losses may vary from 4 per cent to 34 per cent, depending upon
the product and the efficiency of the marketing system (Table 21.
In Recife, in the northeast of Brazil, horticultural crop losses
caused by deficiencies in the commercial marketing system vary
from 7.6 per cent to 40 per cent. In the State of Piaui, in
northern Brazil, 80 per cent of the production of cashew fruit is
lost every year, mainly because the fungus Rhizopus nigricans
attacks the fruit after harvest, and also because the local
market does not have the capacity to absorb all of the fresh
fruit available or to process it for future consumption or
shipment to other markets.

Data obtained in 1973 from the Ministry of Agriculture in
Brazil (Table 3) show the amount of fruits produced and the

TABLE 2. Per Cent Losses during Commercial Handling of
Fruits and Vegetables in Two Major Brazilian Cities, Sao Paulo
(average annual temperature 23°C) and Recife (average annual
temperature 31°C) in Both Wholesale and Retail Markets, 1971

Sao
Paulo

Recife

Wholesale.

Retail

Wholesale

Retail

Fruits

Avocados

27.0

22.0

15.8

9.0

Bananas

33.0

33.0

13.5

12.2

Grapes

18.0

12.0

-

-

Guavas

-

-

36.0

10.0

Lemons

16.0

10.0

18.8

5.0

Oranges

22.0

10.0

14.0

12.7

Papayas

34.0

28.0

16.7

11.4

Peaches

28.0

12.0

-

-

Pineapples

24.0

16.0

11.2

17.1

Watermelons

19.0

22.0

40.0

30.0

Vegetables

Cabbages

19.0

14.0

23.0

27.5

Carrots

15.0

8.0

15.6

15.5

Beets

12.0

7.0

26.1

15.0

Green Beans

19.0

5.0

17.1

17.3

Okra

23.0

8.0

17.7

17.2

Peppers

22.0

10.0

25.4

11.5

Tomatoes

24.0

13.0

7.6

30.0

*Supermarket

TABLE 3. Amounts of Fruit Produced and Estimated
Losses in Brazil, 1973

Fruit

Total production
(metric tons)

Total loss
(metric tons)

%
loss

F Avocados

220,842

22,084

10

Papayas

124,569

24,913

20

Mangoes

682,222

204,697

30

Lemons

82,519

33,008

40

Information obtained from the
Brazilian Ministry of Agriculture. estimated losses that occurred
that year. Losses of potatoes and onions are also high, largely
because of inadequate storage and marketing conditions. Both
tubers are very susceptible to poor handling procedures; they are
exposed to rodents, bacteria, etc., that cause rot. Losses as
high as 30 per cent are reported for both products. For onions,
the major problem is that the varieties cultivated in many
regions of the country, particularly in the northeast, do poorly
in this environment. They have a very low percentage of total
solids after harvest, do not store well under unfavourable
conditions, and spoil easily during handling and transport to the
market.

A survey made by the Brazilian
Financing Commission (CFP) of the Ministry of Agriculture showed
that 5 - 20 per cent losses occur in cereal grains during storage
in both warehouses and silos. An average loss of 6 per cent was
reported for cereals bought and stored by the CFP, and the major
causes were (a) excess moisture content; (b) insect infestation;
(c) inadequate stacking; and (d) inadequate packaging materials.
A research paper published in 1970 by the Federal University of
Vicosa-Minas Gerais, states that loss in weight of corn attacked
by insects and rodents during storage on the farm reached 12 per
cent after a period of three to seven months. Similar losses in
corn weight have been reported from Zambia, Nigeria, Ethiopia,
and India. Even in developed countries such as the United States
and Germany, millions of dollars are lost in the value of stored
cereals after harvest, indicating the complexity of the problem.

THE ROLE OF RESEARCH INSTITUTIONS

Studies in Brazil point out that
the main causes of horticultural and cereal crop losses are
inadequate harvest techniques, lack of, and inadequate, storage
facilities, and poor transportation, handling, and packaging
practices. Obviously, more knowledge about the magnitude and true
nature of the losses is required, and approprate technology to
reduce them should be utilized wherever it is possible.

Although appropriate technology
has been the subject of a growing volume of literature, the term
is open to multiple in the context of "intermediate" or
"low-cost" technologies. However, the term does not
refer to a specific technology, but to a concept. Appropriate
technology is the one that will contribute most to the economic
and social objectives of development in a given situation.

It is crucial that research
institutions become involved in doing what they can to alleviate
the problem. It is necessary to determine the true nature of the
problem in each case and establish precise methodology for
solving it. "ITAL" is the acronym for the Food
Technology Institute of the Secretary of Agriculture for the
State of Sao Paulo, Brazil. In the past ten years, it has been
active in conducting post-harvest research with the objective of
transferring the results to farmers as well as government
agencies. The following studies are in progress.

1. Storage of Maize at the Farm Level

Maize is grown in most of the
states of Brazil, usually on small and medium-sized farms. It is
a product that is nearly always stored on the farm for use as
animal feed. It is, therefore, the cereal that suffers the
highest losses during storage from insects, micro-organisms, and
rodents. Without any doubt, the poor storage facilities and
obsolete procedures for the storing of maize in rural areas
contribute to these high losses. The adoption of bulk storage
systems in metal or concrete bins would be one solution, but
implies a relatively high initial investment not always within
reach of the small farmer. For such cases, a low-cost storage
system with no need for specialized manpower for its construction
is highly desirable.

The storage of grain in
underground pits is one of the oldest systems known, used since
remote times in South Asia. In Malta, grain is traditionally
stored in large vase-shaped underground pits lined with straw. In
Israel, Donahaye and co-workers improved this system by lining
the pits with polyethylene sheets. They obtained good results
with rye stored for 15 months. These researchers consider rodents
as the possible limiting factor for this type of storage.

Underground pits allow hermetic
storage conditions. The principle is that decreasing the
concentration of oxygen and increasing that of carbon dioxide via
respiration of grain and of insects eventually cause the insects
to become inactive, and will sometimes kill them. Experiments
have demonstrated that either a reduction in oxygen or an
increase in carbon dioxide will kill insects within hours or
days, depending on the concentrations of oxygen and CO,, the
insect species, and on factors such as temperature and moisture
content in the grain. It is also known that the degree of
hermetic sealing required to prevent growth of fungi is much more
critical than that needed to control insects in dry grain, where
light infestation can sometimes be tolerated.

An experiment was set up to see
whether fumigated, de husked maize with low moisture content
could be successfully stored in an underground pit lined with
locally available, fairly thin polyethylene. This system was
developed for use on small farms. Three tons of maize were stored
in a pit 2 m x 1.4 m and 1.5 m deep in well-drained red lathosol
soil. The floor was covered with Malathion-treated maize straw 15
cm thick to protect the plastic sheet from abrasion and also to
provide an additional buffer against moisture. The pit was then
lined with a plastic sheet 8 x 7 m and filled with maize.

Hermetic conditions were attained
as follows: The edges ah of the plastic sheet along the shorter
(1.40 m) sides of the pit were folded toward the inside and the
edges on the 2 m sides were pulled together and folded once very
close to the level of the grain. A 2 m steel bar 3/8 inch in
diameter was placed at each side of the folded plastic, and the
bars and plastic were fixed by clamps set 20 cm apart for the
length of the bar. A layer of rice husks 20 cm thick was put on
top of the bin, over which a second plastic sheet 4 x 3.5 m was
placed in order to achieve better thermal insulation. The upper
surface was rounded to avoid rainwater infiltration, and, because
of the slope of the ground, a small U-shaped channel was
constructed around the bin to catch rainwater. No live insects
were detected when the pit was opened for inspection after eight
months of storage. The initial 4.6 per cent of insect-damaged
grains did not increase during the storage period. The moisture
content remained constant and uniform throughout the storage
period, and no condensation accumulated at any point of contact
between the grain and the plastic sheet. The initial temperature
of the maize was 27.2°C. The average final temperature, taken at
five different points in the maize, was 26.9°C ( minimum
observed 26.2°C, maximum 27.5°C). As there was no moisture
migration, it can be assumed that there was no significant
temperature variation during the storage period.

Grains, as living organisms,
breathe and are subject to chemical and biological
transformations that modify their composition. The intensity of
such transformations is directly related to the storage
conditions, length of storage, and insect infestation and
microflora. The retention of germination capacity and the low
increase in free fatty-acid level during the eight months of
storage in this experiment is attributable to slow grain
metabolism resulting from the low moisture content and relatively
stable temperature (27°C). The estimated cost for this kind of
storage pit is:

$Cr*

$US

Human
labour

250

12.5

Plastic
sheets: pit lining

470

23.5

cover for
pit

120

6.0

Closure
system (clamps, etc.)

140

7.0

980

49.0

* $us - equals approximately 20
cruzeiros.

It was found that harvested maize
with a moisture content of 12 per cent, fumigated and stored in
an underground pit lined with a plastic sheet, retained good
characteristics during a storage period of eight months. When the
pit was opened, the maize was found to have its natural colour,
odour, and texture. There were no changes in either moisture
content or germination capacity. The small chemical changes
observed did not damage the quality of the oil in the stored
maize.

2. Aerobic Storage for Preservation of Soybeans in
Silos

Brazil is the world's second
largest producer of soybeans, with a production of 12.5 million
metric tons in the 1976/77 harvest. In contrast to the widely
disseminated maize production, the production of soybeans is
concentrated in the southern part of the country, where only two
estates produce more than 80 per cent of the total soybean crop.
The evolution of soybean production has occurred largely over the
past six years, with the area cultivated increasing from 1.3
million hectares in 1970 to 6.6 million hectares in 1977. The
average yield increased from 1143 kg/ha to 1760 kg/ha in the same
period. Soybean production is increasing in Brazil because it is
teased on modern agricultural technology, it uses genetically
sound seed, and is carried out primarily on very large farms.
However, from the beginning, there was an obvious lack of an
infra-structure to store this huge volume of soybeans.

Co-operatives were organized and,
through government help, existing storage facilities were
improved and new ones were built. Large silos began to appear
with a capacity for storing from 30,000 to 100,000 metric tons of
soybean in bulk. To maintain the quality of the stored soybeans,
aeration systems were installed to force air through the silos
and avoid the risk of rapid aging caused by rising temperature.

Research work was carried out at
ITAL with two metal cylindrical silos, one aerated, one not.
After six months in the aerated silo the beans had a better
quality than those stored in the non-aerated one. The humidity
level dropped from 12.7 to 10 in the same period in the aerated
silo. The free fatty-acid content (as oleic acid) in the beans
rose from 0.3 - 0.4 to 0.6 - 0.7 after ten months of storage in
the aerated unit, while it reached a level of 1.2 to 1.3 in the
beans stored for ten months in the non aerated unit.

This year in the State of
Paraná, silos are under construction that will hold 40,000
metric tons of soybeans. These silos are being coupled with an
aeration system powerful enough to provide a current of air at
the rate of 10 me/ in/ton Soybeans should enter the units with 16
per cent humidity and lose 2 per cent after four months of
storage. The average yearly temperature and relative humidity for
Paraná are 22 C and 8 per cent, respectively, with large
deviations.

Soybeans in non-aerated silos
have been found to have a moisture content of 12 per cent.

If, by introducing aeration to
the storage system, we can r, consistently maintain a 14 per cent
moisture content in soybeans, this would mean a gain in weight of
0.02 x 40,000, or 800 metric tons. With a market price of
soybeans at $US 200/ton, 800 x $US 200 = $US 160,000. This saving
would be enough to pay for installation of the aeration system,
which costs about $US 100,000.

The above data show that in the
case of soybean storage, aerated silos may be the appropriate
technology to adopt in order to avoid losses in both quantity and
quality of a crop that has a high monetary value.

Storing Tahitian and Sicilian
lemons at low temperature in a controlled atmosphere containing
gibberellic acid showed that the fruit could be kept for at least
six months with minimum weight losses.

Similar studies were made with
avocados. Methods for proper storage and ripening of bananas, and
post-harvest control of fungi that attack mangoes have also been
successfully developed and contribute significantly to minimize
post-harvest losses of these fruits.

Some studies have been done for
private companies, mainly on installation of storage and cooling
chambers for fruits and vegetables.

Although horticultural crops may
not be considered to be as important as grain crops, their
nutritional and economic values should not be neglected.

CONCLUSIONS

ITAL's experience in Brazil and
through bilateral projects with other countries has led us to the
following conclusions.

1. Post-harvest technology from
developed countries can be more easily adapted in developing
countries than industrialized agricultural technology can.
2 Government programmes related to post-harvest handling, and
government extension services, can help to transmit post-harvest
technology to the final user.
3. International co-operation for post-harvest technology
transfer can be more effective when research institutes are
directly involved.
4. Improvements in post-harvest handling would greatly benefit
the final consumer in terms of product quality, price, and
availability of food.